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From: "pobrn at protonmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c++/105667] [C++20] lambas in template argument sometimes
 causes an ICE (seg fault)
Date: Sun, 04 Sep 2022 17:40:12 +0000
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X-Bugzilla-Type: changed
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c++
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X-Bugzilla-Keywords: c++-lambda, ice-on-valid-code
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D105667

Barnab=C3=A1s P=C5=91cze <pobrn at protonmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pobrn at protonmail dot com

--- Comment #6 from Barnab=C3=A1s P=C5=91cze <pobrn at protonmail dot com> =
---
Another snippet that I believe triggers the same issue:

template<typename>
struct get { };

template<int>
struct thing {
    using T =3D decltype([](auto) { });

    static constexpr auto value =3D [](auto) {
        return get<T>();
    }(0);
};

thing<0> X;

---

In this case template_parms_to_args() is called with a nullptr.

template_parms_to_args (parms=3D0x0) at /usr/src/debug/gcc/gcc/cp/pt.cc:4912

tsubst_template_decl (t=3D0x7ffff7177280, args=3D<optimized out>, complain=
=3D3,
lambda_fntype=3D0x7ffff717b738) at /usr/src/debug/gcc/gcc/cp/pt.cc:14543

tsubst_lambda_expr (t=3D<optimized out>, args=3D0x7ffff7171d80, complain=3D=
3,
in_decl=3D0x7ffff7173800) at /usr/src/debug/gcc/gcc/cp/pt.cc:19855

tsubst_copy_and_build (t=3D<optimized out>, args=3D0x7ffff7171d80,
complain=3D<optimized out>, in_decl=3D0x7ffff7177000, function_p=3D<optimiz=
ed out>,
integral_constant_expression_p=3Dfalse) at /usr/src/debug/gcc/gcc/cp/pt.cc:=
21446

tsubst (t=3D0x7ffff71760a8, args=3D0x7ffff7171d80, complain=3D3,
in_decl=3D0x7ffff7177000) at /usr/src/debug/gcc/gcc/cp/pt.cc:16400

tsubst_template_args (t=3D0x7ffff7171a20, args=3Dargs@entry=3D0x7ffff7171d8=
0,
complain=3Dcomplain@entry=3D3, in_decl=3Din_decl@entry=3D0x7ffff7177000) at
/usr/src/debug/gcc/gcc/cp/pt.cc:13580

[...]

---

GCC 12.2.0, but GCC trunk on Compiler Explorer also exhibits the same issue=
 (as
do GCC 11.1, 11.2, 11.3, 12.1, and 12.2)=